DIY dDNS service script using Hetzner's DNS API

update-ddns.rb

#!/usr/bin/env ruby
# on OpenRC systems, place into e.g. /etc/periodic/15min
# (or create /etc/periodic/1min and add line to root's crontab)
# on systemd systems, install it as a timer

# create/find these in Hetzner's DNS admin interface at https://dns.hetzner.com/
API_TOKEN_NAME="..."
API_TOKEN="..."

ZONES=["...", "..."] # TLD; must be registered at https://robot.hetzner.com/domain
RECORDS=["...", "..."] # list of subdomains, also specified there
API_BASE = "https://dns.hetzner.com/api/v1"

# will make the script return a little faster if specified
# ZONE_ID="..."
# RECORD_ID="..."

require 'json'
require 'socket'
require 'net/http'
require 'optparse'

def GET(uri)
  headers = {
    "Auth-API-Token" => API_TOKEN,
    "Accept" => "application/json"
  }
  Net::HTTP.get(URI(uri), headers)
end

def POST(uri, body)
  headers = {
    "Auth-API-Token" => API_TOKEN,
    "Accept" => "application/json",
    "Content-Type" => "application/json"
  }
  res = Net::HTTP.post(URI(uri), body, headers)
  res.body
end

def PUT(uri, body)
  uri = URI(uri)
  hostname = uri.hostname

  req = Net::HTTP::Put.new(uri)
  req["Auth-API-Token"] = API_TOKEN
  req["Accept"] = "application/json"
  req.body = body
  req.content_type = 'application/json'
  res = Net::HTTP.start(hostname, uri.port, :use_ssl => true) do |http|
    http.request(req)
  end
  res.body
end

def main(zone_id, record_id)
  ZONES.each do |zone|
    zone_id ||= (
      json = JSON.parse(GET("https://dns.hetzner.com/api/v1/zones"))
      zones_json = json.delete('zones')
      zones_json.find{|x| x['name'] == zone}['id']
    )

    json = JSON.parse(GET("https://dns.hetzner.com/api/v1/records?zone_id=#{zone_id}"))
    records_json = json.delete('records')

    current_wan_ip = Socket.getifaddrs
                       .map{|iface| [iface.name, iface.addr.ip_address] if iface.addr.ipv4? if iface.addr}
                       .compact
                       .find{|x| x[0]=='ppp0'}[1]
    if record_id then
      data = JSON.generate({
          "value": "#{current_wan_ip}",
          "ttl": 60,
          "type": "A",
          "name": "#{record}",
          "zone_id": "#{zone_id}"
      })
      PUT("https://dns.hetzner.com/api/v1/records/#{record_id}", data)
    else
      RECORDS.each do |record|
        record_json = records_json.find{|x| x['name']==record}
        url = "https://dns.hetzner.com/api/v1/records"
        data = JSON.generate({
            "value": "#{current_wan_ip}",
            "ttl": 60,
            "type": "A",
            "name": "#{record}",
            "zone_id": "#{zone_id}"
        })
        record_id ||= record_json['id'] # must exist!
        if record_id then
          PUT("https://dns.hetzner.com/api/v1/records/#{record_id}", data)
        else
          POST("https://dns.hetzner.com/api/v1/records", data)
        end
      end
    end
  end
end
  
def test(zone_id, record_id)
  puts zone_id
  puts record_id
  puts GET("https://httpbin.org/get")
  puts POST("https://httpbin.org/post", JSON.generate({foo: "bar"}))
  puts PUT("https://httpbin.org/put", JSON.generate({foo: "bar"}))
end

options = {}
OptionParser.new do |parser|
  parser.banner = "Usage: update-ddns.rb [options]"

  parser.on("-t", "--test", "Run tests") do |v|
    options[:test] = v
  end
  parser.on("-z ZONE", "--zone ZONE", "Specify zone id") do |v|
    options[:zone_id] = v
  end
  parser.on("-r RECORD", "--record RECORD", "Specify record id") do |v|
    options[:record_id] = v
  end
end.parse!

if options[:test] then
  test(options[:zone_id], options[:record_id])
else
  main(options[:zone_id], options[:record_id])
end